A method for fast 3D tracking using tuned fiducial markers and a limited projection reconstruction FISP (LPR‐FISP) sequence

Abstract

This work demonstrates the feasibility of using wireless, tuned fiducial markers with a limited projection reconstruction-fast imaging with steady-state free precession sequence (LPR-FISP) to accurately obtain tracking information necessary for interactive scan plane selection in magnetic resonance imaging (MRI). The position and orientation of a rigid interventional device can be uniquely determined from the 3D coordinates of three fiducial markers mounted in a known configuration on the device. Three fiducial markers were tuned to the proton resonant frequency in a 0.2T open MR scanner and mounted to the surface of a cylindrical water phantom. An LPR-FISP sequence was developed to suppress the water phantom signal while preserving that of the fiducial markers through a nonselective low-tip-angle excitation and a dephaser gradient applied prior to data acquisition. A localization algorithm was developed to accurately calculate the 3D coordinates of the fiducial markers using four LPR-FISP projections in two orthogonal scan planes. Index terms: interventional MRI; active tracking; fiducial markers; projection reconstruction; radial FISP; device localization MAGNETIC RESONANCE (MR)-GUIDED DEVICE tracking has become an important research area for development of new MR technology that will provide a variety of important capabilities in the future. One key component of current tracking methods is the ability to automatically define an appropriate MR imaging (MRI) scan plane. This feature reduces the time and patient risk associated with interventional procedures. Frameless stereotactic systems have been developed to provide interactive scan plane selection by measuring the position of fiducial markers or light emitting devices (LEDs) mounted onto the surface of a rigid interventional device (1-4). The navigational wands are considered to be less cumbersome than conventional reference frames and articulation arms (5,6). However, optical frameless stereotactic tracking systems have been criticized because they suffer from a number of important limitations. First, they require a line of sight between the markers and the detection system. Second, this requirement hinders positioning of the detection systems within the scan room, which in turn restricts the range of motion of the physician during the procedure. Third, these stereotactic detection systems also add additional (and potentially expensive) components to an already congested physical environment. And finally, they require calibration between the tracking system and the MRI coordinate frames.In this work, a new tracking method is proposed that combines wireless tuned fiducial markers, a limited projection reconstruction-fast imaging with steadystate precession pulse sequence (LPR-FISP), and a marker localization algorithm. Device tracking and interactive scan plane selection is possible by determining the 3D coordinates of the fiducial markers when a minimum of three fiducial markers are mounted onto a rigid interventional device (e.g., biopsy needle). The syst...

Real‐time catheter tracking and adaptive imaging

“…This concern may necessitate some hardware design changes if this system is to be used with human patients. Possible solutions include detuning the tracking markers during RF transmit (19), inserting coaxial chokes along the conductive leads (20), or using inductively-coupled fiducial markers which eliminate the need for conductive leads (12). In these trials, no detuning was used, and no apparent heating effects were noted postmortem.…”

“…The Dumoulin et al (11) method using a single coil requires three projections for determination of the catheter position; the multicoil method by Flask et al (12) requires eight projections for determination of both catheter position and orientation. These localization projections are collected prior to the acquisition of each set of image data.…”

Wireless Accelerometer for MRI-Guided Interventional Procedures

“…In contrast, active tracking gives the operator direct instrument control with immediate feedback under real-time MR image guidance. A number of active tracking techniques have been developed, including optical tracking with an infra-red camera and mirrors [14,15] and also the use of MR micro-receiver coils within the device to induce local inhomogeneities within the magnetic field [16][17][18]. Although optical tracking provides a wireless approach, it requires line-of-sight access for accurate guidance which can be problematic in many MR scanner designs.…”

Undersampled projection reconstruction for active catheter imaging with adaptable temporal resolution and catheter‐only views

“…Tracking of microcoils (13,24,25), involving imaging of bright spots, has also been achieved using PR with just a few projections (26,27). The present investigation differs from previous studies in that PR was employed with greater undersampling factors, active catheters combined with anatomy were imaged, and adjustable temporal resolution was employed.…”